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using System;
using Org.BouncyCastle.Crypto.Utilities;
namespace Org.BouncyCastle.Crypto.Engines
{
/**
* A class that provides CAST6 key encryption operations,
* such as encoding data and generating keys.
*
* All the algorithms herein are from the Internet RFC
*
* RFC2612 - CAST6 (128bit block, 128-256bit key)
*
* and implement a simplified cryptography interface.
*/
public sealed class Cast6Engine
: Cast5Engine
{
//====================================
// Useful constants
//====================================
private const int ROUNDS = 12;
private const int BLOCK_SIZE = 16; // bytes = 128 bits
/*
* Put the round and mask keys into an array.
* Kr0[i] => _Kr[i*4 + 0]
*/
private int []_Kr = new int[ROUNDS*4]; // the rotating round key(s)
private uint []_Km = new uint[ROUNDS*4]; // the masking round key(s)
/*
* Key setup
*/
private int []_Tr = new int[24 * 8];
private uint []_Tm = new uint[24 * 8];
private uint[] _workingKey = new uint[8];
public Cast6Engine()
{
}
public override string AlgorithmName
{
get { return "CAST6"; }
}
public override void Reset()
{
}
public override int GetBlockSize()
{
return BLOCK_SIZE;
}
//==================================
// Private Implementation
//==================================
/*
* Creates the subkeys using the same nomenclature
* as described in RFC2612.
*
* See section 2.4
*/
internal override void SetKey(
byte[] key)
{
uint Cm = 0x5a827999;
uint Mm = 0x6ed9eba1;
int Cr = 19;
int Mr = 17;
/*
* Determine the key size here, if required
*
* if keysize < 256 bytes, pad with 0
*
* Typical key sizes => 128, 160, 192, 224, 256
*/
for (int i=0; i< 24; i++)
{
for (int j=0; j< 8; j++)
{
_Tm[i*8 + j] = Cm;
Cm += Mm; //mod 2^32;
_Tr[i*8 + j] = Cr;
Cr = (Cr + Mr) & 0x1f; // mod 32
}
}
byte[] tmpKey = new byte[64];
key.CopyTo(tmpKey, 0);
// now create ABCDEFGH
for (int i = 0; i < 8; i++)
{
_workingKey[i] = Pack.BE_To_UInt32(tmpKey, i*4);
}
// Generate the key schedule
for (int i = 0; i < 12; i++)
{
// KAPPA <- W2i(KAPPA)
int i2 = i*2 *8;
_workingKey[6] ^= F1(_workingKey[7], _Tm[i2], _Tr[i2]);
_workingKey[5] ^= F2(_workingKey[6], _Tm[i2+1], _Tr[i2+1]);
_workingKey[4] ^= F3(_workingKey[5], _Tm[i2+2], _Tr[i2+2]);
_workingKey[3] ^= F1(_workingKey[4], _Tm[i2+3], _Tr[i2+3]);
_workingKey[2] ^= F2(_workingKey[3], _Tm[i2+4], _Tr[i2+4]);
_workingKey[1] ^= F3(_workingKey[2], _Tm[i2+5], _Tr[i2+5]);
_workingKey[0] ^= F1(_workingKey[1], _Tm[i2+6], _Tr[i2+6]);
_workingKey[7] ^= F2(_workingKey[0], _Tm[i2+7], _Tr[i2+7]);
// KAPPA <- W2i+1(KAPPA)
i2 = (i*2 + 1)*8;
_workingKey[6] ^= F1(_workingKey[7], _Tm[i2], _Tr[i2]);
_workingKey[5] ^= F2(_workingKey[6], _Tm[i2+1], _Tr[i2+1]);
_workingKey[4] ^= F3(_workingKey[5], _Tm[i2+2], _Tr[i2+2]);
_workingKey[3] ^= F1(_workingKey[4], _Tm[i2+3], _Tr[i2+3]);
_workingKey[2] ^= F2(_workingKey[3], _Tm[i2+4], _Tr[i2+4]);
_workingKey[1] ^= F3(_workingKey[2], _Tm[i2+5], _Tr[i2+5]);
_workingKey[0] ^= F1(_workingKey[1], _Tm[i2+6], _Tr[i2+6]);
_workingKey[7] ^= F2(_workingKey[0], _Tm[i2+7], _Tr[i2+7]);
// Kr_(i) <- KAPPA
_Kr[i*4] = (int)(_workingKey[0] & 0x1f);
_Kr[i*4 + 1] = (int)(_workingKey[2] & 0x1f);
_Kr[i*4 + 2] = (int)(_workingKey[4] & 0x1f);
_Kr[i*4 + 3] = (int)(_workingKey[6] & 0x1f);
// Km_(i) <- KAPPA
_Km[i*4] = _workingKey[7];
_Km[i*4 + 1] = _workingKey[5];
_Km[i*4 + 2] = _workingKey[3];
_Km[i*4 + 3] = _workingKey[1];
}
}
/**
* Encrypt the given input starting at the given offset and place
* the result in the provided buffer starting at the given offset.
*
* @param src The plaintext buffer
* @param srcIndex An offset into src
* @param dst The ciphertext buffer
* @param dstIndex An offset into dst
*/
internal override int EncryptBlock(
byte[] src,
int srcIndex,
byte[] dst,
int dstIndex)
{
// process the input block
// batch the units up into 4x32 bit chunks and go for it
uint A = Pack.BE_To_UInt32(src, srcIndex);
uint B = Pack.BE_To_UInt32(src, srcIndex + 4);
uint C = Pack.BE_To_UInt32(src, srcIndex + 8);
uint D = Pack.BE_To_UInt32(src, srcIndex + 12);
uint[] result = new uint[4];
CAST_Encipher(A, B, C, D, result);
// now stuff them into the destination block
Pack.UInt32_To_BE(result[0], dst, dstIndex);
Pack.UInt32_To_BE(result[1], dst, dstIndex + 4);
Pack.UInt32_To_BE(result[2], dst, dstIndex + 8);
Pack.UInt32_To_BE(result[3], dst, dstIndex + 12);
return BLOCK_SIZE;
}
/**
* Decrypt the given input starting at the given offset and place
* the result in the provided buffer starting at the given offset.
*
* @param src The plaintext buffer
* @param srcIndex An offset into src
* @param dst The ciphertext buffer
* @param dstIndex An offset into dst
*/
internal override int DecryptBlock(
byte[] src,
int srcIndex,
byte[] dst,
int dstIndex)
{
// process the input block
// batch the units up into 4x32 bit chunks and go for it
uint A = Pack.BE_To_UInt32(src, srcIndex);
uint B = Pack.BE_To_UInt32(src, srcIndex + 4);
uint C = Pack.BE_To_UInt32(src, srcIndex + 8);
uint D = Pack.BE_To_UInt32(src, srcIndex + 12);
uint[] result = new uint[4];
CAST_Decipher(A, B, C, D, result);
// now stuff them into the destination block
Pack.UInt32_To_BE(result[0], dst, dstIndex);
Pack.UInt32_To_BE(result[1], dst, dstIndex + 4);
Pack.UInt32_To_BE(result[2], dst, dstIndex + 8);
Pack.UInt32_To_BE(result[3], dst, dstIndex + 12);
return BLOCK_SIZE;
}
/**
* Does the 12 quad rounds rounds to encrypt the block.
*
* @param A the 00-31 bits of the plaintext block
* @param B the 32-63 bits of the plaintext block
* @param C the 64-95 bits of the plaintext block
* @param D the 96-127 bits of the plaintext block
* @param result the resulting ciphertext
*/
private void CAST_Encipher(
uint A,
uint B,
uint C,
uint D,
uint[] result)
{
for (int i = 0; i < 6; i++)
{
int x = i*4;
// BETA <- Qi(BETA)
C ^= F1(D, _Km[x], _Kr[x]);
B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
}
for (int i = 6; i < 12; i++)
{
int x = i*4;
// BETA <- QBARi(BETA)
D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
C ^= F1(D, _Km[x], _Kr[x]);
}
result[0] = A;
result[1] = B;
result[2] = C;
result[3] = D;
}
/**
* Does the 12 quad rounds rounds to decrypt the block.
*
* @param A the 00-31 bits of the ciphertext block
* @param B the 32-63 bits of the ciphertext block
* @param C the 64-95 bits of the ciphertext block
* @param D the 96-127 bits of the ciphertext block
* @param result the resulting plaintext
*/
private void CAST_Decipher(
uint A,
uint B,
uint C,
uint D,
uint[] result)
{
for (int i = 0; i < 6; i++)
{
int x = (11-i)*4;
// BETA <- Qi(BETA)
C ^= F1(D, _Km[x], _Kr[x]);
B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
}
for (int i=6; i<12; i++)
{
int x = (11-i)*4;
// BETA <- QBARi(BETA)
D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
C ^= F1(D, _Km[x], _Kr[x]);
}
result[0] = A;
result[1] = B;
result[2] = C;
result[3] = D;
}
}
}
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